Invasive Plants

Found around the park and the surrounding region these plants pose a serious threat to our local ecosystem.

Click on a plant or topic below to learn more about it!

Japanese Barberry (Berberis thunbergii)

Burning Bush or Winged Euonymus (Euonymus alatus)

Bradford Pear (Pyrus calleryana)

Wineberry (Rubus phoenicolasius)

Multiflora Rose (Rosa multiflora)

Chemical Warfare

Autumn Olive (Elaegnus umbellata)

Bush Honeysuckle (Lonicera tatarica, L. maackii, L. morrowii)

Evil Alliances

Japanese Barberry (Berberis thunbergii)

It is recognizable with oblong red berries and large spines (relative to the plant) on the stems of the bush. One thing that makes them a very successful invasive is their root system. The roots are shallow but the plant produces lots of them, 3x more than native blueberry, allowing it to take in more nutrients giving it a competitive edge. It is especially dangerous because it alters the chemistry of the soil. It changes soil pH and alters nutrient levels to benefit its own growth but when left unchecked it can change the soil composition in a very large area negatively impacting native species. Another scary fact about Japanese barberry is that ticks are found in higher populations because the plant creates a humid microclimate that the ticks like.

So, Why is it Here?

Japanese Barberry was brought over as an ornamental from China and Japan in the 1860s.

What You Can Do?

DO NOT PLANT
Care must be taken to remove the entire root system to prevent resprouting.
Hand pulling can be effective for seedlings and young plants
Spread the word! Talk to friends and neighbors about the dangers of invasive plants.

Burning Bush or Winged Euonymus (Euonymus alatus)

This plant displaces important native plants, like spicebush, maple leaf viburnum, and other shrub layer plants. Without those important native shrubs, the local wildlife population struggles for important resources.
It grows earlier in the season than some natives, getting a head start on growing in prime real estate and stocking up on important nutrients to last longer into the winter.
Isn't as appealing to local wildlife.
Spreads quickly, easily, and in large numbers. Forming dense thickets and covering large areas of the forest floor.

So, Why is it Here?

Winged Euonymus was brought to our region as an ornamental plant. It was introduced in 1860, as an exotic and beautiful landscaping plant. It gained popularity due to its vibrant color, late in the fall season. Despite it being known to be highly invasive, while some state have banned Euonymus alatus, many still are allowed to be sold and planted. It is unfortunately commonly used in commercial and residential landscaping here in northern DE, allowing it to spread in great numbers into our parks and other natural spaces. The seeds from these plants can easily be carried (by wind, water or wildlife) into parks where they take root and grow.

Due to its hardiness, and high quantities, Euonymus alatus can be very difficult to remove.

What You Can Do?

DO NOT PLANT
Pull seedlings
Cut mature plants and spray stumps (don't let chemical sprays run off into the soil!!)
Spread the word! Talk to our local garden center, encourage them to stop selling it. Talk to friends and neighbors about the dangers of invasive plants.

What Could You Plant Instead?

Euonymus atropurpureus, Eastern Wahoo

A native Euonymus, that also produces beautiful fall color!
Blossoms beautiful flowers in spring (unlike Euonymus alatus)
The charming shape of the flowers and fruit gave it the nickname "hearts bursting with love"!
Provide good resources to local wildlife.

Bradford Pear (Pyrus calleryana)

Takes over land and prevents important native plants, like grasses, flowering meadow plants, and other grassland plants from growing.
They spread easily and very very quickly. A new sapling can take root in a garden and displace intended plants within a year of the garden being planted.
The strong roots of this tree take hold deep and are extremely difficult to remove even as barely grown saplings.
As adults these tree's branch structure is very unstable and tight. Making them highly susceptible to storm damage. This makes having them near structures rather dangerous.
Often they are reported to smell very poorly when their flowers bloom in spring.

So, Why is it Here?

In the early 1900's the pear industry in the Western US (California and Oregon) was suffering due to disease (fire blight). So a mission was set out to find another pear tree from elsewhere that could be used to breed a pear tree resistant to the blight. The callery pear tree was found in China, and was tested and found to be successful. They were very hardy, often found growing in poor soil conditions and environments other trees wouldn't.

Some time later, in the early 1950's, a horticulturist at the U.S. Plant Introduction Station in Glenn Dale named John L. Creech decided that the callery pears had a greater potential than simply help the pear orchards. He envisioned the trees as the perfect street tree. With its good looks, and hardy disposition, it seemed like just the thing to landscape anything from suburban streets to shopping centers with. He bestowed upon his specimen the name Bradford. This new 'perfect' pear tree was planted all across the continental US. Cheap, easy, and pretty; nearly every town, highway, or home had a desire to line their streets with these flowering trees.

Unfortunately, the specimen selected for mass-production was hiding a few terrible flaws. The limbs are poorly structured and prone to breaking apart. What was initially thought to be a sterile tree, turned out to able to quickly and easily reproduce. The bradford pear could now (late 1900's to present) escape its carefully crafted street placement and spread far and wide into old fields, parks, and other natural spaces. Many places have now banned the bradford pear from being planted. But they still spread and are seen every growing season.

What Can You Do?

DO NOT PLANT
Remove any you have, pull saplings and cut adults.
Plant native trees instead!

What Can You Plant Instead?

Prunus serotina, Black Cherry

Also produces white flowers in spring, similar in shape and size to bradford pears.
Produce an abundance of berries which are great for wildlife.
Trees are very sturdy and can withstand and adapt after major weather events.

Wineberry (Rubus phoenicolasius)

Wineberry grows in dense, twisting thickets that then crowd out native ground cover species like native blackberry. Its known for its bright red, thorny stem and edible berries.
A single wineberry cane can grow up to nine feet long. The canes will then twist together to make spiny thickets that are impenetrable to both humans and wildlife.
Not only does it spread through seed dispersal, wineberry is capable of growing through a process called tip-rooting. Tip-rooting happens when the tip of one of the canes of wineberry arches back to the ground creating a new base for roots to develop which causes more canes to grow.

So, Why is it Here?

Wineberry was introduced from Asia in the 1890s to aid in commercial raspberry and blackberry production. It was to be cross pollinated with other raspberry plants to produce a plant that would produce a greater crop. It is still used today by berry breeders and it does very well in gardens; however, once it escapes its plot and makes it into the natural ecosystem it is very hard to control. It is now considered an invasive species across much of the mid-Atlantic region as far west as Tennessee.

What Can You Do?

Plant native berry plants in your garden, NOT wineberry.
Pulling or digging out wineberry can be sucessful because the plant does not have an extensive underground root strategy. (But be sure to wear heavy gloves!)
Spread the word about this species and encourage garden centers and nurseries to stop selling this plant.

What Can You Plant Instead?

Aronia arbutifolia, Red chokeberry

Native alternative that provides edible berries for humans and wildlife
While it does tend to grow in thickets, chokeberry does not have thorns so it is better to have in your forest or yard.

Multiflora Rose (Rosa multiflora)

Multiflora rose produces a lot of seeds and many of them survive. Studies have found that one plant can produce up to 500,000 seeds per year and those seeds can stay viable for 10-20 years in the soil bank.
This plant has virtually no predators that feed on or kill the plant. This allows it to grow unchecked and take over where its planted. It produces berries late in the summer that persist through winter which provides food for birds but allows the seeds to be spread over large areas.
The plant leaves out earlier than many native plants, allowing it to store up extra nutrients to help out compete the natives. This also allows it to last longer into the cold season
It is shade tolerant but often invades sunny areas like open woodlands and along trail sides.

So Why is it Here?

Multiflora rose was introduce in this region in the late 1700's as an ornamental plant. It was said that it could also be used for erosion control, as a living fence in agriculture fields, and as a food source for local wildlife. Unfortunately like many non-native plants it was not successful in those mission, and instead grew wildly out of control, forming dense thickets crowding out native plants.

What Can You Do?

DO NOT PLANT
Remove what you can by hand pulling and cutting, before it fruits in late summer.
Spread the word

What Can You Plant Instead?

Swamp Rose, Rosa palustris

Native rose shrub, produces lovely flowers, without taking over
Great for wetter soil. Our area is becoming more and more prone to flooding, so this might be an idea plant.

Chemical Warfare

Several invasive plants produce chemicals in their leaves, fruits, or roots that prevent neighboring, often native, plants from being able to grow. These chemicals can inhibit photosynthesis preventing the victim from being able to produce the sugar it needs to survive. Allelopathy helps the invasive get ahead because it reduces the competition they would face if the native was healthy and photosynthesizing properly.

Plants that use allelopathy include autumn olive and the various species of bush honeysuckle.

Autumn Olive (Elaegnus umbellata)

Autumn olive forces out native plants when it grows by shading them out with its dense foliage and changing the soil chemistry through allelopathy.
Attempts to remove this shrub through cutting it down or doing a controlled burn to kill off the plant actually cause the plant to sprout more.
The roots of the autumn olive plant have nitrogen-fixing nodules. This allows the plant to create its own nitrogen making it possible for it to survive in even the worst quality soils.
This plant is a master seed producer, a single plant is capable of producing 200,000 seeds a year!

So, Why is it Here?

Autumn olive was introduced in 1830 from Asia. It was brought over to be an ornamental plant for landscaping that would also provide food and shelter for wildlife. It was once believed to be one of the best plants to prevent soil erosion so the Soil Conservation Service planted it along ridges and roads to keep soil in place. This allowed the plant to spread out of control as the birds would carry seeds from the berries to other locations where the plant could grow.

What can you do?

Pull seedlings before they have the chance to establish their sturdy root system
Unfortunately, herbicides are the only option once the tree has grown too large to be pulled. Just be cautious if using them to not allow the chemicals to run off into the surrounding area
Do not plant this in your garden and spread word about its impacts to friends and local garden centers

What can you plant instead?

Viburnum acerifolium, Maple leaf viburnum

This plant is a popular food source for the local wildlife
Its gets its name from the leaves that resemble maple tree leaves. Just like a maple tree the leaves on this shrub turn a lovely red color in the fall
In the spring, little white flowers bloom on the ends of branches

Bush Honeysuckle (Lonicera tatarica, L. maackii, L. morrowii)

This bush is very aggressive, dominating wherever it is planted.
Releases chemical that impedes photosynthesis in nearby plants impeding their growth to reduce competition.
Easy to spot in the winter time because its leaves remain green well into the fall after most of the other native species have dropped their leaves.
There are three species widespread throughout Delaware: Amur, Tartarian, and Morrow’s.
Their dense thickets covering the forest floor and shrub layer, can cause long term damage to the forest. Their shade can prevent new saplings and sprouts of native plants, including important trees.
Birds eat the shrub's berries but they do not provide the high-fat, nutrient-rich fruits that migrating birds need.
Because it begins to grow leaves so early in the spring, it can often disturb or prevent from growing ephemeral spring flowers, that would grow only shortly in the early spring sun in the forest.

(Photo taken 12-1-21)

So, Why is it Here?

Like many invasive shrubs, the Bush Honeysuckle was brought to our region in the mid-18th and 19th century as an ornamental plant. Praised for its flowers and fruit's visual appeal, it was cultivated in botanical gardens. It also began to be planted as a wildlife habitat and for erosion control. Despite being poorly suited to either task. Wildlife don't get the nutrients they need from the fruit. And their root and branch structure isn't helpful in soil stability.

Unfortunately, like many invasive shrubs they can be difficult to remove, in part because of their large numbers.

What Can You Do?

Do Not Plant
Remove if in your property by pulling young plants, and digging out mature plants. The roots need to be fully removed so that they do not regrow.
Plant native to replace them!

What Can You Plant Instead?

Spicebush, Lindera benzoin

Native to DE, spicebush is a favorite among the BCSP wildlife.
The host plant for the spicebush swallowtail butterfly!
Has a lovely scent to the leaves when rubbed.
Great source of food for the birds (but not for people, do not eat!).

Evil Alliances

Climate change is helping these invasive plants spread even more! As temperatures rise as a result of climate change native plants may not be able to survive the new atmospheric conditions. This makes room for more invasives to come in and take over where the natives no longer live. Many of the invasive species listed above are very drought tolerant. It is likely that climate change will bring on longer periods of dry weather that native plants are not adapted to deal with allowing the invasives to prevail. Drier periods bring greater chances for wildfires where plants like Autumn olive and Bradford pear will be the first to establish in an ecosystem and push out natives before they even have the chance to establish themselves.

The invasive species above have come from another continent and been able to establish them selves with great success. They are very hardy, adaptable species that have withstood a complete change in their ecosystem, they will have a better chance of surviving the environmental transformations that will occur as climate change continues. These plants will be allowed to wreak further havoc and alter the landscape of our local ecosystems pushing out native plants and the wildlife that depends on them.

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